Homebuilt Rov Forum

Exploring the Hobby of Building your own ROV - Imagine, Create, Inspire.
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PostPosted: Aug 3rd, 2017, 5:26 pm 
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Joined: Nov 28th, 2011, 11:24 am
Posts: 121
I've been looking at various different foams for bouyancy.
sometimes you can find the datasheet for the foam you have, in which case look at the compression strength...
Kingspan insulation has a compression strength of > 140kpa at 10% compressed, this equates to about 14m water depth so it's not ideal. it also absorbs water. :-(
Mine is skinned with fibreglass gellcoat which should help strength and water absorbtion.

I also looked at EVA foam (the wife's yoga bricks) but it compresses at much lower pressures.

One simple way to test your foam if you don't have the datasheet is to stand on a sample and see if it crushes.
The critical bit is cutting the right size of sample.

Lets say I weigh 200Lbs in my clothes and boots, (i'm not that big but it makes the maths easy) and say I want to dive to 30M water depth, thats about 43psi but lets call it 50psi for easy maths.
so 200Lbs divided by 50psi = 4 square inches, so cut a piece of foam 2"x2" (by say 1" thick, but thickness is not critical).

So now you stand on you sample of foam with all your weight on it and see if it crushes, simples.
You can do the maths for your own weight and depth to work out what area you need to cut your sample to.

Hope that helps someone.
BBB.


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PostPosted: Aug 8th, 2017, 3:47 am 
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Joined: Nov 28th, 2011, 11:24 am
Posts: 121
Following on from this....
I saw a video the other day of a Ping-Pong ball being depth tested on an ROV, It survived down to 94m them imploded quite spectacularly.
When the remains came back up the plastic was compressed so much it had turned brittle, like an egg shell.
quite an impressive test. :-)


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